Endocrine Abstracts

Background: Gestational diabetes insipidus (DI) is a rare complication of pregnancy, usually developing in the last trimester and resolves spontaneously 4–6 weeks post-partum. It is mainly caused by excessive vasopressinase activity, an enzyme expressed by placental trophoblasts which metabolises arginine vasopressin (AVP). However in some cases, it can develop in a patient who had limited reserve of ADH and marginal central DI prior to pregnancy and may not resolve after delivery. Herein we represent a case of DI developed in pregnancy and consisted after delivery due to ectopically located neurohypophysis.

Case: 24 year old female patient admitted to our clinics with the complaints of polyuria and polydipsia. The amount of daily consumed water was 18 l. The complaints were started in the last 2 months of pregnancy and did not resolve in 2 years after delivery. She did not have any previously diagnosed psychiatric illness such as obsessive compulsive disorder, somatization or depression. She did not have history of head trauma or symptom or sign of any pituitary hormone deficiency. She was not using any drugs which could be related with DI. In the basal biochemistry, the serum Na level was 143 mmol/l, serum osmolarity was 293 mosm/l. The urine osmolarity was 93 mosm/l. Anterior pituitary hormone levels were normal except mildly elevated prolactin (29 ng/ml). She was hospitalized for water deprivation test. During the test, urine osmolarity did not change with water deprivation but became %200 concentrated after vasopressin which was compatible with cental DI. In the pituitary MRI neurohypophyseal T1-bright spot situated ectopically in the infundibulum. Desmopressin nasal sprey was started and the symptoms resolved immediately.

Conclusion: Gestational DI is a rare complication of pregnancy occurring in two to four out of 100,000 pregnancies. It usually develops at second half of pregnancy and remits spontaneously 4–6 weeks after delivery. Serum and urine osmolality are required for the diagnosis, but other tests such as serum sodium, glucose, urea, creatinine, liver function may be informative. The water deprivation test is normally not recommended during pregnancy because it may lead to significant dehydration, and should be dane in the post partum priod. After delivery pituitary MRI should be performed at some point to exclude lesions in the hypothalamo-pituitary region.